Metal nitrate explosives containing mononitrated aromatic sensitizing agents



United States Patent M METAL NITRATE EXPLOSIVES CGNTAENENG MONONITRATED ARGMATIC SENSI'I'EZENG AGENTS Edwin M. Scott, 3n, Glendale, Calif. (Pill. Box 323, Tuiunga, Calif.) No Drawing. Filed Feb. 28, 1961, Ser. No. 92,161 3 Claims. (Cl. 149-67) The present invention relates to inexpensive, readily manufactured, stable and powerful explosive compositions. More particularly the present invention relates to easily handled detonatable mixtures of a dry nondetonatable metal nitrate and a non-detonatable sensitizing agent.

Since Nobels basic discoveries in the nineteenth century in the high explosive field, much effort has been expended towards development of inexpensive, powerful explosive compositions. The basic ingredient utilized by Nobel in his explosive compositions (commonly known as dynamite) was nitroglycerine.

However, the nitroglycerine content of dynamite made it a relatively expensive explosive and since it was known that ammonium nitrate alone would detonate as a high explosive, Nobel soon developed his extra dynamite series which replaced a substantial part of the nitroglycerine in dynamite with ammonium nitrate. Such explosives found extensive use in coal mines because of their low explosion temperatures. Because of the known explosive characteristics of ammonium nitrate, many efforts were directed to the development of an inexpensive high explosive which did not contain nitroglycerin. Although many ammdnium nitrate explosives not containing nitroglycerin were developed, it was not until the early 1930s that the successful Nitrarnon type was invented which overcame the problems of low sensitivity and water resistance which made the earlier mixtures unsuccessful. More recently loose, unpackaged ammonium nitrate-fuel oil mixtures have been successfully used in large diameter boreholes.

Despite the fact that ammonium nitrate explosives not containing nitroglycerine have been known for nearly 100 years, and despite the many efforts to develop other inexpensive high explosives, at present the ammonium nitratecombustible mixtures are the most economical source of high explosive energy. (See Cook, The Science of High Explosives, page (1958).) However, more important, despite much effort the prior art has been unable to develop an inexpensive, easily handled high explosive from non-detonatable components. All presently known inexpensive high explosives contain either nitroglycerin 3,178,325 Patented Apr. 13, 1965 in the composition of this invention as non explosives in Table 1.2 on page 4.

It should be noted that this same table lists ammonium nitrate as a secondary high explosive. In addition to utilizing non-detonatable, stable and inexpensive components, the compositions of the present invention are easily handled so the ordinary techniques presently employed in using explosives in the field may be employed. Another advantage of the present invention is that the inexpensive metal nitrate component is used in high concenrations in all compositions.

In general the present invention is an easily manufactured, inexpensive high explosive consisting essentially of an intimate mixture of virtually anhydrous, nondetonatable alkali metal or alkali earth metal nitrate (in the range of about to by weight) and a nondetonatable, combustible, organic, sensitizing agent. The sensitizing agent may be either a solid or. a liquid but if a liquid sensitizing agent is used then it is normally necessary that it be combined with a gelling agent in order to insure intimate contact with the metal nitrate and inhibit stratification and non homogeneity. Unlike ammonium nitrate, the normally used commercial metal nitrates do not usually absorb liquid sensitizers. The sensitizing agent itself may also act as a gelling agent, or a gelling agent may be added.

. An object of the present invention is an easily handled inexpensive detonatable composition made from nondetonatable components.

Another object of the present invention is the utilization of inexpensive non-detontatable metal nitrates in high concentration in a high explosive composition with only non-detonatable sensitizing agents.

Still another object of the present invention is to formulate a high explosive composition from sodium nitrate or calcium nitrate and liquid alkyl hydrocarbons, liquid aromatic hydrocarbons or mononitroaromatic hydrocarbons.

Other objects and advantages of this invention will be readily apparent from the following description in which is set forth exemplary embodiments of this invention.

The major ingredient of the explosive composition of the present invention is a metal nitrate which is normally non-detonatable. While any alkali metal nitrates such as sodium nitrate and potassium nitrate and any alkali earth metal nitrates such as calcium nitrate, barium nitrate and strontium nitrate may be used, it is preferred to. use sodium nitrate and calcium nitrate for reasons of economy and superior performance, particularly when compared to the known detontable ammonium nitrate. Commercial grades of grained or granular sodium nitrate such as Arcadian and of spherical particles such as Chilean sodium nitrate have been found satisfactory and similarly commercial grained calcium nitrate is satisfactory; It is important that the metal nitrate be vritually anhydrous i.e. it should contain less than 2% moisture and preferably less than 0.5% moisture. However, the commercial grades of sodium nitrate and calcium nitrate are normally sold in substantially anhydrous form so such products can be used directly in the present invention. Commercial sodium nitrate and calcium nitrate which has a particle size range of about 6 mesh to 60 mesh and bulk density of about 1.4 has been found satisfactory for use in the present invention so the material need not be classified into a narrow particle size range. Preferably the metal nitrate should not be coated with an inorganic coating agent, such as kieselguhr since such coating renders it more insensitive and results in very inferior performance.

The concentration of the metal nitrate in the explosive composition must be sufficiently high so that sufiicient oxygen is present to complete the combustion of the sensitizing agent. Preferably the concentration of the metal nitrate should be such that the explosive composition as a Whole has an approximate zero oxygen balance; however, the concentration of the metal nitrate can vary somewhat from that required for an exactly zero oxygen balance and in practice a 2%-3% variation gives satisfactory results. Table I below gives some representative compositions by weight percent of metal nitrate, sensitizing agent and gelling agent.

Another important ingredient of the explosive composition of the present invention is a non-detontable, combustible sensitizing agent. It has been found that out of the many non-detonatable, combustible sensitizing agents, organic compounds such as the alkyl hydrocarbons, the aromatic hydrocarbons and the mononitroaromatic hydrocarbons give much better results. Common alkyl hydrocarbons such as petroleum, waxes, asphalts, coal tar may be used; however, the best results to date have been obtained with the diesel oil known as Class 2 Diesel Fuel Oil. Likewise any of the common aromatic hydrocarbons such as benzene, toluene, xylene and naphthalene may be used and they all produce satisfactory results. However it has been found that the mononitroaromatic hydrocarbons such as nitrobenzene, nitrotoluene and nitronaphthalene produce exceptionally good results. The best example is paranitrotoluene which produces an outstanding explosive composition.

An important feature of the present invention is that the metal nitrate and the sensitizing agent are maintained in intimate contact to obtain the best results. In the case of a solid sensitizing agent such as a paranitrotoulene, the particles of metal nitrate and sensitizing agent may simply be mechanically mixed to obtain such intimate contact. However, although liquid sensitizing agents may be mechanically mixed with the metal nitrate, they tend to separate from the metal nitrate after such mixing since the commercial granular metal nitrates such as sodium nitrate are not porous and do not absorb liquids as does ammonium nitrate. Consequently with liquid sensitizing agents such as diesel oil, it has been found necessary to add a gelling agent so that mechanical mixing produces a stable, gelled intimate and homogeneous mixture. The gelling agent must be compatible with the sensitizing agent so that it will form a stable, gelled mixture with it and the metal nitrate. Such result may be achieved by either having the gelling agent dissolve in the sensitizing agent or having the gelling agent absorb the sensitizing agent. Various metal salts of fatty acids have been found to be satisfactory gelling agents such as sodium, calcium, zinc, and magnesium sterate and barium laurate. Also ammonium stearate and ammonium lignin sulfonate may be used. However, the aluminum fatty acid salts such as aluminum octoate, aluminum stearate or naphthenates and aluminum palmitate produce superior results. Such aluminum fatty acid salts may be obtained commercially under the trade name of Special Gelling Agent X628 sold by Nuodex. Other gelling agents which give much better results are various forms of cellulosic material. Examples of such cellulosic material are coal, starch, wood flour, sawdust, and chips of Wood such as cork and balsa. It should be noted that the gelling agent also functions as a sensitizing agent in that it aids the strength of the explosion. For example, the metal nitrate may be mixed solely with wood flour and detonated. However, gelling agents such as cel'lulosic material are relatively poor sensitizing agents since they substantially decrease the density of the composition, and the maintenance of a high density is desirable, although the presence of minute air bubbles also appears desirable.

Extensive comparative test data has been obtained with respect to the detonatable compositions of the present invention which although it is much cheaper illustrate its superiority over ammonium nitrate and ammonium nitrate-diesel oil mixtures. In addition the comparative test data illustrates the superiority of particular compositions of the present invention. The test data was obtained by boring holes, 18 inches deep and 6 inches in diameter, in a uniform moist clay deposit in the Mojave Desert in San Bernardino County, California, which has been extensively used for similar explosive tests. Each hole was loaded with 1500 grams of explosive composition in a polyethylene bag and /3 pound of a highly brisant Propelex booster. The explosive composition was made by first mechanically mixing the sensitizing agent and gelling agent until a gelled mixture was formed. The metal nitrate particles were then dispersed throughout the gelled mixture by mechanically mixing. The Propelex booster is a standard booster which contains trinitrotoluene, trinitrohexamethyltetramine and pentaerythritol tetranitrate and develops a detonation pressure of about 4,000,000 p.s.i. The holes were thoroughly backfilled and tamped and the booster was then detonated. The diameter of the crater formed by the blast was then measured. Extensive experience with this deposit has shown that the results are highly reproducible because of the uniform nature of the deposit. Consequently the results give excellent test data with respect to the comparative strengths of various explosive compositions. Table II infra gives some representative test data with respect to compositions of the present invention as compared to each other and to ammonium nitrate compositions. For each test, the ingredients of the explosive composition are given by weight percent. The final number is the strength of the explosive composition. The strength number is obtained by entering the diameter of the crater created by the explosion in the empirical formula 3.7511 where d is the diameter in feet. Such empirical formula is based on a series of tests with dynamite in this deposit and is known to be a reliable, reproducible measure of the strength of an explosive.

Table II 1 Nitrate (wt. percent) sensitizing agent Gelling agent Strength (wt. percent) (wt. percent) HERCULES GRAINED (1) NH NO3 (100)-. (0)-. 975 (2) NIIJNOB (94.5) Diesel oil (5.5) (0)-. 1,563

CHILEAN (3) NaNO (94.5) Diesel 011 (5.5)- (0). 638 (4) NaNOa (88.1) Diesel oil (11.9) (0).- 1,107 (5) NaNOs (88.1) Diesel oil (11 9) Alkaterge O 2 (0.0119) 1,249 (6) NaNOa (87).- Diesel oil (11.7)-.- X-628 (1.3) 1,736 (7) NaNOa (88.1) Diesel oil 1) X-628 3 (1 8) 1, 736 (8) NaNOa (90)-. Diesel oil (9 X-628 3 (1)..-. 1,591 Diesel oil (10.7) Al oetoate (l 2)- 1,736 Diesel oil (11 8)--. Al octoate (O 1). 1, 480 Diesel oil (10. Ba laurate (1 2) 1, 427 Diesel oil (11.7) Ca stearate (1.3) 1, 401 Odorless kerosene (9.8) Na lignin sulionate (6.2). l, 401 Odorless kerosene (11.52). Oleio acid (0.24) 1,5 1 Diesel oil (5.5). 1,401 Diesel oil (9.1). 1, 736 1). 2,083 1, 508 2, 083 2,083 2,116 (22) NaNOa (75.1). 1,827 (23) NaNOa (86.7). 2,149 (24) NaNOs (86.9) 2, 083 (25) NaNOa (87.0) 1, 952 (26) NaNOs (83.8) 1, 563 (27) NaNOs (83.9) 2,083 (28) NaNO; (84.1)- Xylene (9.7) 2,184 (20) NaNO (84.5). Methyl naphthalene (9.3) 2,083 (30) NaNO; (86.5). Naphthalene (13.5)"-.- 1,677 (31) NaNO (76.9).-- Nitrobenzene (169).- 1,920 (32) NaNOa (76.0) Nitrobenzene (16,9) Starch (7.1) 2, 049

comrnncrxr.

(33) Ca(N0 (76.4) Nitrobenzene (17.3) Wood flour (6.3) 2,149 (34) KNO (79.9) Nitrobenzene (14.7) Sawdust (5.4) 2, 541

CHILEAN (35) NaNOa (78.3) Orthonitrotoluene (15.5)"-.. Wood flour (6.2) 2,184 (36) NaNO (78.3) l\4etanitrotoluene (15.5) Wood flour (6.2). 2, 323 (37) NaNOa (78.3)... Paranitrotoluene (15.5) Wood flour (6.2)- 2,049 (38) NaNO (79.4) Paranitrotoluene (20.6) (0) 2,616

1 Propelex booster alone has a strength of 284. 2 A surface active agent sold by Commercial Solvents.

3 Commercial mixture of aluminum fatty acid salts sold as Special Gelling Agent X-028 by Nuodex.

The test data in Table II points out several significant features of the present invention. First, it should be noted that when using diesel oil as a sensitizing agent, the sodium nitrate composition has substantially greater strength when preferred gelling agents are employed such as the aluminum fatty acid salts and Wood chips or sawdust. Also such superiority is maintained although the concentration of the sodium nitrate is varied from the concentration which gives an overall zero oxygen balance in the composition as a Whole. However, the choice of a particular gelling agent has a substantial effect on the strength of the explosive composition. For example, even the choice of metal in the fatty acid metal can significantly affect the explosive strength. The use of aromatic hydrocarbons in place of alkyl hydrocarbons such as diesel oil increases the strength of the composition and the use of mononitroaromatic hydrocarbons increases it even more. Also the use of solid sensitizing agents increases the strength so that when a solid mononitroaromatic hydrocarbon is used as a sensitizing agent, truly outstanding results are obtained.

The following theory may explain Why solid sensitizing agent improves the results obtained by the present invention and the choice of a cellulosic material gelling agent for a liquid sensitizing agent has a substantial effect 0n the results. Such theory should be regarded as merely a probable explanation for some of the unusual and unexpected results achieved by the present invention and not as a limitation upon the invention. It is believed that detonation is initiated by compression of minute air spaces of about 1 1O to l 10 cm. radius in the explosive, hence the presence of many such minute air spaces is conducive to detonation. The use of a solid sensitizing agent or a preferred gelling agent such as the porous cellulosic material with a liquid sensitizing agent increases the number of such minute air spaces and consequently increases both the brisance and strength of the explosion. The test data shown in Table III tends to support this theory. The test data in Table III was obtained in exactly the same way as Table 11 except that the mechanical mixing of first the liquid sensitizing agent and the gelling agent and second the gelled mixture and the metal nitrate was carefully varied rather than being the same for each explosive composition. In test 1, the entrainment of air was minimized while in test 2, the entrainment of air was maximized.

T able Ill Metal nitrate sensitizing agent Gelling agent Strength (wt. percent) (wt. percent) (wt. percent) CHJCLEAN (1) NZlNOs (88.1) Diesel oil (10.7)..-- X-G28 (1.2).--. 1,648 (2) NaNOa (88.1) Diesel oil (107).... X-628 (1.2)--.. 1,984

In addition, although very successful results have been obtained using metal nitrmes with particle sizes in the range of about 6 to 60 mesh, it is preferable that smaller particle sizes should be used such as less than 100 mesh or, even better, less than 200 mesh. Such smaller particles sizes permit the metal nitrate to hold liquid sensitizing agents much better and make the explosive composition more sensitive. While the composition of this invention is composed essenially of non-explosive components, the inventive concept herein disclosed is not avoided or departed from by the addition of minor amounts of explosive constituents which do not materially affect the characteristics. It should be noted that to obtain detonation of the composition of the present invention it is necessary to utilize a highly brisant booster such as Propelex and Pen-tolite. Thus normally the booster would have to develop a detonation pressure above 2,000,000 p.s.i. However with the more sensitive compositions such as those containing mononitroaromatic hydrocarbons, detonation may be achieved with lower detonation pressures such as those achieved by several sticks of 40% dynamite. While the test data has been obtained primarily by only one sensitizing agent in each explosive composition, mixtures of sensitizing agents may be used. For example, where an alkyl hydrocarbon such as diesel oil is used as the sensitizing agent, the explosive composition could be made more sensitive by addition of a small proportion of a superior sensitizing agent such as the mononitroaromatic hydrocarbons to the diesel oil.

It will be understood that the foregoing description and test data are only illustrative of the present invention and it is not intended that the invention be limited thereto since many other specific embodiments of the present invention will be obvious to one skilled in the art in view of this disclosure. All substitutions, alterations, modifications and variations of the present invention which come within the scope of the following claims or to which the present invention is readily susceptible without departing from the spirit and scope of this disclosure are considered as part of the present invention.

I claim: 1. A detonatable explosive composition consisting of non-detonable components and consisting essentially of a nitrate chosen from the group consisting of sodium nitrate, calcium nitrate, barium nitrate, strontium nitrate, and potassium nitrate, and mixtures thereof; a mononitroaromatic chosen from the group consisting of nitrobenzene, orthonitrotoluene, metanitrotoluene, paranitrotoluene, and nitronaphthalene, and mixtures thereof; and from 0% to 10% by weight of the total composition of a substance selected from the group consisting of coal, charcoal, W001, cork, and starch, and mixtures thereof; said nitrate and said mononitroar-omatic being present in such proportions as to give an oxygen balance for said composition between the limits of 3% and 3%. 2. The composition in accordance with claim 1 Wherein the nitrate is sodium nitrate.

3. The composition in accordance with claim 1 wherein the nitrate is calcium nitrate.

References Cited by the Examiner UNlTED STATES PATENTS 674,291 5/01; Blomen l49105 X 1,305,846 6/19 Waller 149-105 X 2,325,064 7/43 Lawrence 149-62 X 2,398,071 4/46 Barab '149-7 2,680,067 6/54 Davidson l49-62 X 2,768,073 10/56 Davidson 149-45 CARL D. QUARFORTH, Primary Examiner.

LEON D. ROSDOL, Examiner. 

1. A DETONATABLE EXPLOSIVE COMPOSITION CONSISTING OF NON-DETONABLE COMPONENTS AND CONSISTING ESSENTIALLY OF A NITRATE CHOSEN FROM THE GROUP CONSISTING OF SODIUM NITRATE,CALCIUM NITRATE, BARIUM NITRATE, STRONTIUM NITRATE AND POTASSIUM NITRATE, AND MIXTURES THEREOF; A MONONITROAROMATIC CHOSEN FROM THE GROUP CONSISTING OF NITROBENZENE, ORTHONITROTOLUENE, METANITROTOLUENE, PARANITROTOLUENE, ANDNITRONAPHTHALENE, AND MIXTURES THEREOF; AND FROM 0% T 10% BY WEIGHTOF THE TOTAL COMPOSITION OF A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF COAL, CHARCOAL, WOOD, CORK, AND STARCH, AND MIXTURES THEREOF; SAID NITRATE AND SAID MONONITROAROMATIC BEING PRESENT IN SUCH PROPORTIONS AS TO GIVE AN OXYGEN BALANCE FOR SAID COMPOSITION BETWEEN THE LIMITS OF -3% AND 3%. 